A typical loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles, such as trucks and trailers. To compensate for height differences between the loading dock platform and an adjacent bed of a truck or trailer, many loading docks have a dock leveler. A typical dock leveler includes a deck or ramp that is pivotally hinged along a back edge to vary the height of a front edge. A retractable extension plate or lip pivots or translates outward from the deck's front edge to span the gap between the rear of the truck bed and the front edge of the deck. The deck and lip provide a bridge between the dock's platform and the vehicle's bed so that personnel and material handling equipment can readily move on and/or off the vehicle during loading and/or unloading operations.
To help prevent the vehicle from accidentally or prematurely departing from the dock, some loading docks have a vehicle restraint with a hook-like barrier that can be selectively moved between a raised blocking position and a lowered release position. In the blocking position, the barrier engages a front edge of a vehicle's RIG (rear impact guard) to help restrain the vehicle at the dock. The vehicle restraint releases the vehicle by lowering the barrier to a release position below the RIG. A RIG or rear impact guard (also known as an ICC bar) is a horizontal bar at the rear of the vehicle and is situated several inches below the vehicle's truck/trailer bed. The primary purpose of a RIG is to help prevent an automobile from underriding a truck or trailer in the event of a rear end collision.
Many dock leveler installations have a pit in which the deck can descend to a cross-traffic position where the upper surface of the deck is generally flush with the platform. While some decks are stored at the cross-traffic position, other dock levelers known as “vertically storing” dock levelers have a pivotal deck that is generally upright when stored. Vertically storing dock levelers are sometimes used in so-called “drive-through” applications. Drive-through applications are loading dock arrangements where the rear cargo doors of a vehicle can be swung open about the vehicle's rear vertical door hinges after the vehicle has already been backed into the dock and properly positioned for loading and unloading operations.